With the progress of technology, electronic devices are becoming increasingly advanced and capable of performing a variety of tasks. Users of electronic devices such as mobile phones, laptops, PDAs etc. are always on the move and wireless communication is exceedingly important for the mobile professional. Users want to be connected to other people, send and receive emails, browse the internet and perform several other functions while on the move.
To perform the functions stated above, the amount of data that needs to be transmitted from a transmitting station with multiple transmitting antennas to receiving stations is ever increasing. In wireless communications, the performance of a system (i.e. the rate of transmission, the error rates, etc.) is dependent on the quality of the transmission channel. The quality of the transmission channel changes constantly and therefore wireless communications systems provide services for varying data rates to allow for these changing transmission conditions.
For this purpose a process called link adaptation is carried out where based on the feedback received from the receiving station, different transmission schemes can be implemented. For example, schemes that support faster transmission can be implemented when the channel conditions are relatively good and slower transmission schemes with greater redundancy can be used when the channel characteristics are relatively poor. However, this link adaptation needs to be done on an ongoing basis to determine the characteristics of the channel, in order to enable the best modes of transmission.
Conventional systems used only two transmit and two receive antennas. However, with the growing demand of higher and more reliable data rates, multiple-input-multiple-output systems that support multiple transmit antennas and multiple receive antennas are being developed. The process of performing link adaptation for any number of transmit antennas connected to any number of receive antennas is currently not known. Alamouti and Pure Spatial Multiplexing are one of the few transmission schemes that optimize data transmission in two transmit and two receive antenna networks.
Thus there is a need to generalize the process of link adaptation for any number of transmit and receive antennas that provide ways of determining the most efficient data transmission schemes.